The invention relates to a 12-pulse converter (i.e. a converter operating on 12 half-cycles), with a polyphase autotransformer for converting an alternating current (AC) supply into a direct current (DC) supply.
The field of application is particularly that of control systems for electric motors, in particular for electrically controlled equipment in an aircraft, such as the thrust reversers of an airplane.
In such applications, it is known to make an electric motor control system of the type comprising a converter, an inverter, and an input filter for the inverter.
FIG. 10 shows a converter 101 whose output is connected via an input filter 145 to an inverter 141 for the purpose of varying the speed of a motor 143 depending on requirements.
The input filter 145 comprises a smoothing choke 147 and a capacitor 149. The smoothing choke 147 serves to filter the DC supply output from the converter 101. It also serves to limit and smooth the current drawn by the capacitor 149 when the circuit is switched on. In addition, the smoothing choke 147 serves to limit harmonic rejection associated with the switching of the inverter 141.
In general, the converter comprises a transformer in a polyphase configuration for reducing the kVA rating of the transformer.
A publication by Choi et al. entitled “Polyphase transformer arrangements with reduced kVA capacities for harmonic current reduction in rectifier-type utility interface” (Vol. 11, No. 5), published by IEEE in September 1996, describes a converter comprising an autotransformer having a primary winding connected in a delta configuration and two secondary windings connected in a star configuration. The two secondary windings of the autotransformer are connected to two rectifier bridges with parallel operation thereof being ensured by two interphase chokes.
In many applications, particularly in aerospace, a problem that needs to be solved is reducing the weight and the volume of electric motor control systems.